"Not once, I never completed 100 percent of the runs before preseason," Kiessling said. "I guess I can disclose it now: You get a heart rate watch which saves all the runs. But since my wife's very athletic she did a couple of runs with that heart rate watch on the cross trainer.

"They were that good that nobody noticed. But when it's time to get back on the pitch, I was always leading the pack."

Kiessling, 34, ended his impressive career in May 2018. At senior level, the attacker only played for two clubs, Nurnberg and Leverkusen, but despite severe hip problems, he made 403 top flight appearances and scored 144 goals.

"I am proud to have reached the 400. Even though it was quite a struggle," Kiessling added. "But these days, I can't carry around my six-year old daughter. I can lift her, but not more. The pain kicks in. It goes into the back, into the legs.

"I am currently looking at whether it makes sense to get an artificial hip. I don't think I have another choice."